1. Field of the Invention
The present invention relates to a liquid ejection head, a method of manufacturing a liquid ejection head, and an image forming apparatus, and more particularly, it relates to an electronic circuit for controlling liquid ejection, an electrical wiring arrangement and structure, and a method of manufacturing such a structure.
2. Description of the Related Art
As an image forming apparatus in the related art, an inkjet printer (inkjet recording apparatus) is known, which comprises an inkjet printer head (liquid ejection head) having an arrangement of a plurality of liquid ejection nozzles and which records images on a recording medium by ejecting ink (liquid) from the nozzles toward the recording medium while causing the inkjet head and the recording medium to move relatively to each other.
Such an inkjet head of an inkjet printer of this kind has pressure generating units, each comprising, for example, a pressure chamber to which ink is supplied from an ink tank via an ink supply channel, a piezoelectric element which is driven by an electrical signal in accordance with image data, a diaphragm which constitutes a portion of the pressure chamber and deforms in accordance with driving of the piezoelectric element, and a nozzle which is connected to the pressure chamber and from which the ink inside the pressure chamber is ejected in the form of a droplet because of the volume of the pressure chamber being reduced by the deformation of the diaphragm. In such an inkjet printer, an image is formed on a recording medium by combining dots formed by ink ejected from the nozzles of the pressure generating units.
Ink ejection is thus controlled by transmitting electrical signals to the piezoelectric elements that are to be driven, and in order to transmit these electrical signals, electrical wires are provided on the perimeter of the ink tank. Various methods for installing these wires have been proposed in consideration of the various aspects, such as the number of components and the manufacturing costs.
For example, Japanese Patent Application Publication No. 9-314831 discloses an inkjet recording head comprising: a head main body having ink spraying ports and ink supply hole grooves; and a cover member which covers the ink grooves to form a liquid-tight seal. According to the inkjet recording head disclosed in Japanese Patent Application Publication No. 9-314831, it is possible to reduce the number of components and to achieve a simple manufacturing process, and moreover, the number of connections of electrical circuit components can be reduced and manufacturing costs can also be reduced.
Japanese Patent Application Publication No. 9-314833 discloses a method in which electrical signals are supplied to the piezoelectric elements by means of thin film transistors (TFTs). More specifically, electrodes are formed so as to extend to edge faces of drive substrates with which thin film transistors (TFTs) are provided, and the drive substrates are installed in a direction perpendicular to a direction in which piezoelectric elements are formed in such a manner that the electrodes on the edge faces of the drive substrates make contact with electrodes of the piezoelectric elements.
Moreover, Japanese Patent Application Publication No. 11-261186 discloses a structure in which an undulating-shaped mechanical coupling section of a module substrate has contact points and the substrate can be arranged in various directions. The contact points are connected together by means of soldering, brazing or mechanical caulking.
However, in the invention described in Japanese Patent Application Publication No. 9-314831, there is a problem in that since electrical contacts are provided, the reliability of the connections in the contact sections is poor. Furthermore, it is hard to actualize the invention since it is difficult to achieve accurate positioning in the cases of high-density wires. Since the cover member is formed by inflecting a film material, it does not maintain structural strength and does not function as a structural member.
Moreover, in the invention described in Japanese Patent Application Publication No. 9-314833, in compositional terms, it is necessary to connect the electrical wires by placing two substrates in contact with each other, and therefore it is difficult to achieve accurate positioning in cases of high-density wires, thus leading to a loss of reliability in the connections.
Furthermore, in the invention described in Japanese Patent Application Publication No. 11-261186, since there is a great amount of freedom of layout, then there is a merit in that the space can be used efficiently; however, since the connections are made mechanically, then their accuracy depends on the mechanical processing accuracy and hence it is difficult to apply it to high-density wiring.
As described above, it has been proposed that wiring be implemented in a three-dimensional fashion in the peripheral region of an inkjet printer head; however, many of these proposals involve connecting sections located at intermediate points of the wires. Hence, the greater the number of wires, the more difficult it becomes to achieve reliable electrical connections. Moreover, as the density of the wiring increases, the required level of processing accuracy in the materials becomes higher, and accurate positional registration becomes more difficult. This makes it even harder to achieve electrical connections.
Furthermore, in the related art, since the wiring sections are formed by a structure in which a plurality of components are bonded three-dimensionally or are formed by bending a film, then it is difficult to achieve the sufficient rigidity or airtightness of the structure.